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•Global geometry optimizations of the homoclusters of the six PAH molecules.•The magic numbers of the clusters are discussed with their building units.•The cluster structures are ...classified into herringbone and amorphous geometries.•The clusters of prolate molecules tend to take herringbone structures.
Growth sequence patterns of molecular clusters have not been well elucidated. To examine structures of planar-molecule clusters, naphthalene, anthracene, phenanthrene, phenalene, naphthacene, and pyrene clusters with up to 10 molecules were theoretically investigated with the all-atom OPLS potential. The global-minimum geometries of the naphthalene dimer, trimer, and tetramer are consistent with the experimental data, suggesting that the model potential is useful for predicting the cluster geometries. The growth sequence patterns of the naphthalene, anthracene, phenanthrene, and naphthacene clusters are based on herringbone structures whereas the structures of the phenalene and pyrene clusters are amorphous. The magic numbers of the clusters are 7 or 8 except for the phenalene clusters. These numbers are used to discuss structural motifs of the clusters.
This paper is intended to introduce a filtration analysis of sampled maps based on persistent homology, providing a new method for reconstructing the underlying maps. The key idea is to extend the ...definition of homology induced maps of correspondences using the framework of quiver representations. Our definition of homology induced maps is given by most persistent direct summands of representations. The direct summands uniquely determine a persistent homology. We provide stability theorems of this process and show that the output persistent homology of the sampled map is the same as that of the underlying map if the sample is sufficiently dense. Compared to existing methods using eigenspace functors, our filtration analysis represents an important advantage that no prior information related to the eigenvalues of the underlying map is required. Some numerical examples are given to demonstrate the effectiveness of our method.
A geometry optimization method for water clusters (H2O) n was developed in the present study. The method was applied to the TIP3P and TIP4P water clusters in the range of n ≤ 30, and the resulting ...structures were compared with the global-minimum structures in the literature (n ≤ 25 for the TIP3P potential and n ≤ 30 for the TIP4P potential). The method failed to reproduce the previously reported global minimum of the n = 24 TIP4P cluster. However, it was possible to find new global minima for the n = 24, 26−30 TIP3P cluster and the TIP4P clusters of 25, 28, 29, and 30 molecules.
Geometry optimization of carbon dioxide clusters (CO2) n with the size of 4 ≤ n ≤ 40 is performed by a heuristic and unbiased method combined with geometrical perturbations. Comparison with the ...global minima reported in the literature shows that the present method reproduces the global minima for clusters with n = 6, 8, 13, 19, 28, 30, and 32 and yields new global minima for (CO2)23, (CO2)25, and (CO2)35. For the other clusters under investigation, global minima are first reported in this article. Structural features of CO2 clusters and efficiency of the optimization method are discussed.
The Hayabusa2 spacecraft collected samples from the surface of the carbonaceous near-Earth asteroid (162173) Ryugu, and brought them to Earth. The samples were expected to contain organic molecules, ...which record processes that occurred in the early Solar System. We analyzed organic molecules extracted from the Ryugu surface samples. We identify a variety of molecules containing the atoms CHNOS, formed by methylation, hydration, hydroxylation, and sulfurization reactions. Amino acids, aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and nitrogen-heterocyclic compounds were detected, with properties consistent with an abiotic origin. These compounds likely arose from aqueous reaction on Ryugu’s parent body and are similar to organics in Ivuna-type meteorites. These molecules can survive on the surfaces of asteroids and be transported throughout the Solar System.
Carbonaceous (C-type) asteroids
are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of ...carbonaceous chondrites
and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth's atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR)
onboard the spacecraft Hayabusa2
, indicating that the asteroid's boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m
s
K
(300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites
and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect
. We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites
. These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity
of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies
.
Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that ...it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu's parent body.
The uncarboxylated form (ucOC), but not the γ-carboxylated form (GlaOC), of the bone-derived protein osteocalcin stimulates insulin secretion and regulates energy metabolism in insulin target ...tissues. Glucagon-like peptide-1 (GLP-1) is an insulin secretagogue that is released from the gut in response to food intake. We have now found that Gprc6a, a putative ucOC receptor, is expressed in epithelial cells of the mouse small intestine as well as in STC-1 enteroendocrine cells. Secretion of GLP-1 by STC-1 cells was stimulated by ucOC but not by GlaOC. The serum GLP-1 concentration in mice was increased by intraperitoneal or oral administration of ucOC, whereas GlaOC was effective in this regard only after oral application. Serum insulin levels were also increased by ucOC, and this effect was potentiated by an inhibitor of dipeptidyl peptidase IV and blocked by a GLP-1 receptor antagonist. Intravenous injection of ucOC in mice increased the serum GLP-1 concentration, and also increased the serum level of insulin. Our results suggest that ucOC acts via Gprc6a to induce GLP-1 release from the gut, and that the stimulatory effect of ucOC on insulin secretion is largely mediated by GLP-1.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Involvement of the bone matrix protein osteocalcin (OC) in the development of learning and memory, and the prevention of anxiety-like behaviors in mice. However, the direct effects of OC on neurons ...are still unknown comparing to the mechanism how OC affects systemic energy expenditure and glucose homeostasis. In this study, we investigated the effect of OC on proliferation, differentiation, and survival of neurons using the rat pheochromocytoma cell line PC12.
RT-PCR analysis for OC receptor candidates revealed that Gpr158, but not Gprc6a, mRNA was expressed in PC12 cells. The growth of PC12 cells cultured in the presence of 5–50 ng/mL of either uncarboxylated (GluOC) or carboxylated (GlaOC) OC was increased compared to cells cultured in the absence of OC. In addition, NGF-induced neurite outgrowth was enhanced by OC, and H2O2-induced cell death was suppressed by pretreatment with OC. All of these results were observed for both GluOC and GlaOC at comparable levels, suggesting that OC may directly affect cell proliferation, differentiation, and survival by binding to its candidate receptor, GPR158.
•PC12 cells expresses GPR158 but not GPRC6A as a candidate OC receptor.•OC stimulated ERK signaling in PC12 cells.•OC promoted cell proliferation, differentiation, and survival of PC12 cells.•PC12 could be a beneficial tool to investigate the action of OC on neurons in detail.
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